JPH08110683A - Image forming device - Google Patents

Abstract

PURPOSE: To enable the cleaning of a contact electrifying member in a proper state at any time by objectively recognizing the performance of a cleaning member with respect to the contact electrifying member 2 from the relation of the cleaning member 2 with the contact electrifying member 2. CONSTITUTION: The coefficient of dynamic friction of the cleaning member 30 against an image carrier 1 is set higher than that of the contact electrifying member 2 against the image carrier 1, so that the transfer of foreign matter from the electrifying member 2 to the cleaning member 30 can be facilitated and the transfer of the foreign matter from the cleaning member 30 to the electrifying member 2 is suppressed. The quality of the cleaning member 30 is judged on the basis of an objective characteristic by taking notice of the coefficient of dynamic friction against the image carrier 1. Thus, proper quality can be held.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus which charges a surface of an image bearing member by contact with a contact charging member, and more particularly to a contact for efficiently removing foreign matters adhering to the contact charging member. The present invention relates to an image forming apparatus in which a relationship of a dynamic friction coefficient between a charging member and a cleaning member is clarified.

[0002]

2. Description of the Related Art A photosensitive layer on the surface of an image bearing member is uniformly charged by a charging means, optical image information is applied to the photosensitive layer to form an electrostatic latent image, and usually powdery toner is supplied to the electrostatic latent image. An image forming apparatus that repeats the process of electrostatically transferring the toner image onto a sheet-shaped transfer material such as paper after the latent image is visualized,
It is well known that it has been widely put into practical use.

In such an image forming apparatus, it is well known that inorganic photoconductive materials such as selenium, cadmium oxide and zinc oxide are used as the photoconductive material used as the photosensitive layer of the image carrier. However, various organic compounds have come to be used in addition to these in recent years.

Examples of this type of substance include poly-N.
-Organic photoconductive polymers such as vinylcarbazole and polyvinylanthracene, low molecular weight organic photoconductive members such as carbazole, anthracene, pyrazolines, oxadiazoles, hydrazones, polyallyl alkanes, phthalocyanine pigments and azo pigments , Cyanine dyes, polycyclic quinone pigments, berylylene pigments, indigo dyes,
Organic dyes and pigments such as thioindigo dye and squaric acid methine dye are used.

Since these substances are easier to synthesize than the above-mentioned inorganic photoconductive materials and easily form a substance exhibiting photoconductivity in an appropriate wavelength range, they are increasingly used. For example, US Pat. Nos. 4,123,270 and 4
No. 251613, No. 4251624, No. 425682
1, No. 4,260,672, No. 4,268,596, No. 4
JP-A-278747 and JP-A-4293628 disclose that a disazo pigment exhibiting photoconductivity is used for an image carrier as a charge generation layer in a photosensitive layer functionally differentiated into a charge generation layer and a charge transport layer. .

As described above, in the image forming process using the image bearing member, as means for charging the image bearing member, a direct current of 5 to 8 KV is applied to the wire of the charger in which the metal wire is expanded.
There have been many corona discharge type charging means for charging by corona generated by applying a high voltage of a certain degree. However, this type of charging means may generate ozone and nitrogen oxides accompanying corona discharge, which may damage the image carrier itself or may adhere to the image carrier and cause deterioration in image quality. Moreover, the amount of discharge current flowing in the direction of the image carrier is 5 to 3
There was a problem that the efficiency was low, such as about 0%.

Therefore, in order to eliminate such a drawback, a contact charging type charging means has been proposed in recent years in which a charging member (contact charging member) is brought into direct contact with an image carrier. In this method, a charging member formed in the form of a roller, a belt, a blade, or the like is brought into contact with the surface of the image carrier, and a DC voltage or a voltage obtained by superimposing AC on DC is applied to the charging member, thereby Can be charged.

[0008]

The contact charging type charging means has the advantages that ozone and nitrogen oxides are not generated, and that voltage application to the image bearing member is performed efficiently. On the other hand, since the charging member is in contact with the image carrier, foreign matters such as toner and paper dust remaining on the surface of the image carrier are likely to adhere to the charging member, which may cause deterioration in image quality. there were. JP-A-2-301777
In view of this point, the publication discloses a configuration in which a cleaning member made of a felt material is brought into contact with the charging member, and the surface of the charging member is cleaned by the cleaning device.

However, the image forming apparatus described in the above publication focuses only on the material point of view such that the cleaning means for the charging member is made of a felt material, and the cleaning means is different from the contact charging member. The specific criteria for determining what characteristics the relationship should have are not clear. As a result, for example,
When a pad as a cleaning means is commercialized and mass-produced, there is no standard for selecting defective products, and quality retention becomes very vague. In addition, it is not possible to objectively determine the quality of the cleaning means during maintenance, and it is not possible to perform accurate maintenance.

On the other hand, it is also necessary to clarify the criteria for determining what characteristics the contact charging member has in relation to the image bearing member and suppressing the transfer of toner from the image bearing member to the contact charging member. It is important for maintaining the cleaning performance of the contact charging member for a long period of time.

The present invention has been made in view of such circumstances, and objectively grasps the performance of the cleaning member with respect to the contact charging member from the relationship between the cleaning member and the contact charging member, and always keeps an appropriate state. The purpose is to enable cleaning of the contact charging member in the above. further,
It is an object of the present invention to clarify the criterion for suppressing the transfer of toner from the image carrier to the contact charging member in the relationship between the contact charging member and the image carrier, and to maintain the cleaning performance of the cleaning member for a long period of time.

[0012]

In order to achieve the above object, the present invention provides a contact charging member for contacting the surface of an image carrier to charge the surface, and a contact charging member for contacting the surface of the contact charging member. An image forming apparatus including a cleaning member for cleaning the surface, which forms an electrostatic latent image on an image carrier in a charged state, and then visualizes the electrostatic latent image by a developing unit and transfers the electrostatic latent image to a transfer material. The coefficient of dynamic friction of the cleaning member with respect to the image carrier is larger than the coefficient of dynamic friction of the contact charging member with respect to the image carrier.

Further, in the invention of claim 2, the coefficient of dynamic friction of the contact charging member with respect to the image carrier is set to less than 0.4, and the coefficient of dynamic friction of the cleaning member with respect to the image carrier is set to 0.4 or more. It has the property of

[0014]

By making the coefficient of dynamic friction of the cleaning member with respect to the image carrier larger than the coefficient of dynamic friction of the contact charging member with respect to the image carrier, transfer of foreign matter from the contact charging member to the cleaning member is facilitated and the cleaning member From this, it becomes difficult for foreign matter to transfer to the contact charging member, and the cleaning performance can be improved. Moreover, the quality of the cleaning member can be judged based on such objective characteristics, and proper quality can be maintained.

Further, by setting the coefficient of dynamic friction of the contact charging member to the image carrier to be less than 0.4 and setting the coefficient of dynamic friction of the cleaning member to the image carrier to be 0.4 or more, the contact charging from the image carrier is performed. It is possible to suppress the transfer of foreign matter to the member and maintain the cleaning performance of the cleaning member for a long period of time.

[0016]

Embodiments of the present invention will be described below in detail. FIG. 1 is a schematic configuration diagram of a contact charging type image forming apparatus. First, an image forming process of the image forming apparatus will be described with reference to FIG.

Around the image carrier 1 which rotates in the clockwise direction in FIG. 1, a contact charging member 2 which can be contacted and separated from the image carrier 1, an eraser 3, a developing unit 4 and a image carrier 1 which can be separated from each other. Members such as the transfer member 5, the cleaning blade 6, and the charge removing unit 7 are installed. The surface of the image carrier 1 is uniformly charged by the contact charging member 2 in the contact state, and the image is exposed or written by the optical image forming means including the mirror 8.
An electrostatic latent image is formed on the surface. The electrostatic latent image is removed (trimmed) by the eraser 3 from, for example, an electrostatic charge in an area outside the supplied transfer paper size, and reaches the developing step. In the developing step, the developing unit 4 supplies the developer to the electrostatic latent image on the surface of the image carrier 1 to form a toner image.

Next, in the transfer step, the transfer paper supplied from the supply means (not shown) is sent between the image carrier 1 and the transfer member 5 by the registration roller 9 in synchronization with the toner image. The transfer member 5 is biased so that the toner image is transferred onto the transfer paper sandwiched between the transfer member 5 and the image carrier 1. After the transfer step is completed, the surface of the image carrier 1 is wiped of the residual toner image by the cleaning blade 6, and then the residual charge is removed by light exposure from the charge eliminating unit 7. On the other hand, the transfer paper on which the toner image has been transferred is separated from the image carrier 1 and sent to a fixing unit (not shown) via the transport path, where the toner image is fixed on the paper surface and discharged outside the machine.

FIG. 2 is a partial cross-sectional front view showing a structural example of the contact charging member 2 in the image forming apparatus described above. Figure 2
The contact charging member 2 shown in FIG.
A metal rod material such as CC material or Al material is used. Axis 21
An intermediate layer 22 is formed on the outer periphery of the plate with a wall thickness of about 1 to 4 mm. The intermediate layer 22 is made of an electrically conductive powder material (carbon black material, metal powder material, etc.) in a medium resistance elastic body such as epichlorohydrin rubber or synthetic rubber such as silicon rubber, ethylene propylene rubber, nitrile rubber, norbornene rubber. The composition has a volume resistance of 10 ⁵ Ωcm or less, preferably 10 ³ Ωcm or less, and a rubber hardness (JIS A) of 20 to 4 as these characteristics.
The common angle is 5 degrees, preferably 25 to 40 degrees.

On the outer periphery of the intermediate layer 22, the surface layer 2
3 has a layer thickness of 3 to 25 μm, preferably 4.5 to 12 μm. For the surface layer 23, a material such as Lumiflon in which tin oxide is dispersed and mixed, or nylon can be used. The surface layer 23 has a volume resistance characteristic of 10 ⁵ to
10 ¹³ Ωcm, preferably 10 ⁶ to 10 ¹² Ωcm. Further, it is desirable that the volume resistance from the intermediate layer 22 to the surface layer 23 has conductivity of about 10 ⁶ to 10 ¹² Ωcm.

Both ends of the shaft core 21 are rotatably supported by bearings 24, and are pressed against the image carrier 1 by the urging force of a pressing spring 25. The support structure of the contact charging member 2 and the pressure contact structure to the image carrier 1 are not limited to this, and an appropriate friction occurs between the image carrier 1 and the contact charging member 2, and the image carrier It suffices that the contact charging member 2 be rotated together with the rotation of 1.

The power supply means for the contact charging member 2 is applied with a voltage from a power supply 26 whose application timing is controlled by a control means (not shown) to a power supply receptacle 27 in contact with the shaft core 21, so that the shaft core 21, A current flows through the image carrier 1 via the intermediate layer 22 and the surface layer 23 to charge the surface thereof. The power feeding means is not particularly limited in its specific configuration as long as it directly passes the current through the contact charging member 2 to the image carrier 1, and for example, via the pressing spring 25 and the bearing 24. It is also possible to apply the voltage from the power supply 26 to the contact charging member 2.

A cleaning member 30 is in contact with the surface layer 23 of the contact charging member 2 over the entire length as shown in FIG. The cleaning member 30 is formed by adhering an elastic pad 31 to a back plate 32, and contacts the surface layer 23 of the contact charging member 2 with a uniform load by the urging force of the pressing spring 33. It should be noted that the shape of the cleaning member 30 is not limited to the pad shape as shown in the same figure, but any form may be used as long as it has elasticity and contacts the surface layer 23 of the contact charging member 2 with a uniform load. May be Further, in order to prevent the cleaning member 30 from becoming settled, the cleaning member 3 is stopped while the image forming apparatus is stopped.
A contact / separation mechanism for separating 0 from the contact charging member 2 may be provided.

FIG. 3 shows an outline of a method of measuring the dynamic friction coefficient of the contact charging member 2 and the cleaning member 30 which will be described later in an embodiment. In the present invention, the characteristics are grasped by the dynamic friction coefficient of the cleaning member 30 and the contact charging member 2 with respect to the image carrier 1, and the cleaning member 3
The cleaning performance based on 0 is determined.
In Examples described later, the dynamic friction coefficients of the cleaning member 30 and the contact charging member 2 with respect to the image carrier 1 are shown in FIG.
It is measured by the method as shown in.

That is, a tape material 40 having a width of 25 mm prepared by applying the surface agent of the image carrier 1 to a PET sheet is prepared. Regarding the dynamic friction coefficient of the contact charging member 2, the tape material 40 is pressed against the surface layer 23 of the contact charging member 2 with a constant load (100 g in this embodiment), and the dynamic friction coefficient when the tape is pulled in the axial direction is not shown. Measure with a coefficient measuring machine. Regarding the dynamic friction coefficient of the cleaning member 30,
The measurement is performed by pressing the tape material 40 against the pad 31 of the cleaning member 30 instead of the contact charging member 2 by the above method and pulling it in the axial direction.

EXAMPLE A plurality of types of cleaning members 30 having different dynamic friction coefficients μ1 with respect to the image carrier 1 are brought into contact with a plurality of types of contact charging members 2 having different dynamic friction coefficients μ2 with respect to the image carrier 1, and continuous paper feeding is performed. Endurance test was conducted. (A) Used contact charging member Each contact charging member 2 has a structure as shown in FIG. 2, the shaft core 21 is made of SUS material (φ8 × 341 mm), and the intermediate layer 22 is made of epichlorohydrin rubber (thickness 3 m.
m, total length 300 mm). And the surface layer 23
Are made of different materials such as
The contact charging member 2 of B and C was used.

Level A: The surface layer 23 is formed of nylon (trade name: CM80000, manufactured by Toray Industries, Inc.). Level B: The surface layer 23 is formed by dispersing and mixing tin oxide in Lumiflon. Level C: The surface layer 23 was formed by dispersing and mixing Lumiflon and silica in epichlorohydrin rubber. Each of these contact charging members 2 has a volume resistance of 10 ¹¹
The proportion of the mixture and the thickness of the surface layer 23 were adjusted so as to be -10 ¹² Ωcm. Explaining a specific manufacturing method, after the intermediate layer 22 is fixed to the shaft core 21 by a method such as adhesion or press-fitting, the surface of the intermediate layer 22 is polished and finished, and the surface layer is air-sprayed on the surface. It was formed by applying the material forming 23 and drying at a temperature of around 150 ° C. for 45 to 90 minutes.

Table 1 shows the results of measurement of the dynamic friction coefficient μ2 for the image carrier 1 of these levels a, b and c by the method shown in FIG. The numerical value in parentheses in Table 1 indicates the range of variation in the measured values.

[0029]

[Table 1]

(B) Cleaning member used Each cleaning member 30 has a structure as shown in FIG. 2, and the cross section of the pad 31 is length × width = 3 (or 4) × 15 m.
formed to m. Each cleaning member 30 has a pad 31 formed of a material having the following levels a, b, c, and d. Level a: GS felt # K102 (trade name, Toray Industries, Inc.
Level b: Needle felt GG (trade name, manufactured by Nippon Felt Industry Co., Ltd.) Level c: Needle felt GF (trade name, manufactured by Nippon Felt Industry Co., Ltd.) The pad 31 of each of these cleaning members 30 has a thickness. Three
It was made of a single material of mm, and was bonded to the back plate 32 with a double-sided tape to produce the structure shown in FIG. Level d: Non-woven fabric with a thickness of 1 mm (trade name: Lintara, manufactured by DuPont) and a moltoplain material (thickness: 3 m) as an elastic material.
m) were bonded together to form a pad 31. The cleaning member 30 is made of a non-woven fabric, and the surface layer 2 of the contact charging member 2 is
Use it by abutting on 3.

Table 2 shows the results of measurement of the dynamic friction coefficient μ1 with respect to the image carrier 1 at these levels a, b, c and d by the method shown in FIG. The numbers in parentheses in Table 2 are
The variation range of the measured values is shown.

[0032]

[Table 2]

(C) Other test conditions The image forming apparatus used had a structure as shown in FIG. 1, and the image carrier 1 was an organic photoconductor (OPC) of φ80, and the linear velocity of the image carrier 1 was 1. : 120 mm / sec, charging applied voltage:
-1500V, paper passing size: A4, developing method: dry two-component developing, image carrier 1 cleaning method: counter blade method.

The results of the durability test are shown in Table 3. The numerical values in Table 3 are the number of durable sheets until the occurrence of image defects, and when a halftone or black solid image was formed, a state in which white lines appeared parallel to the sheet passing direction was defined as an image defect. When an image defect occurred, black streaks were formed due to toner adhesion at the positions corresponding to the white streaks of the contact charging member 2.

[0035]

[Table 3]

By summarizing the above results, the following things become clear. (I) The dynamic friction coefficient μ1 of the cleaning member 30 with respect to the image carrier 1 is larger than the dynamic friction coefficient μ2 of the contact charging member 2 with respect to the image carrier 1, that is, μ1> μ2. The combinations are as follows. (Cleaning member, contact charging member): (a, b) = (0.42, 0.3), (a, b) =
(0.42, 0.3), (b, b) = (0.45, 0.
3), (b, b) = (0.45, 0.3) As is clear from Table 3, these combinations show that the number of durable sheets exceeds 20,000 and the life is long. It was

(II) The dynamic friction coefficient μ1 of the cleaning member 30 with respect to the image carrier 1 is smaller than the dynamic friction coefficient μ2 of the contact charging member 2 with respect to the image carrier 1, that is, μ1 <μ2. The combination of the members 2 is as follows. (Cleaning member, contact charging member): (a, c) = (0.42, 2.0), (b, c) =
(0.45, 2.0), (c, b) = (0.18, 0.
3), (c, b) = (0.18, 0.3), (c, c)
= (0.18, 2.0), (d, b) = (0.24,
0.3), (d, b) = (0.24, 0.3), (d,
(C) = (0.24, 2.0) As is clear from Table 3, these combinations had a durable life of less than 10000, indicating a short life.

Considering the above results, the fact that the cleaning member 30 has a larger dynamic friction coefficient with respect to the image carrier 1 which is the same member than the contact charging member 2 means that the same member is attached to the contact charging member 2. The same thing can be said of a kimono. That is, since the cleaning member 30 has a larger friction coefficient than the contact charging member 2 with respect to the adhered substances such as toner and paper dust, the adhered substances are the cleaning members 30.
It can be seen that the situation is such that it is apt to be caught in and is transferred to the same member side. Further, the adhered matter transferred to the cleaning member 30 rarely retransfers to the contact charging member 2 side. Therefore, the coefficient of dynamic friction μ1 of the cleaning member 30 with respect to the image carrier 1 is equal to that of the contact charging member 2 of the image carrier 1.
The cleaning performance is improved when the coefficient of dynamic friction is larger than μ2.

From the results of (I) and (II) above,
When the dynamic friction coefficient μ2 of the contact charging member 2 with respect to the image carrier 1 is in the range of 0.2 to 0.4, including the measurement variation, the image carrier 1 in the shaded area on the number line shown in FIG. It can be seen that the cleaning member 30 having the dynamic friction coefficient μ1 exhibits a suitable cleaning effect. That is, for the contact charging member 2 having a dynamic friction coefficient μ2 with respect to the image carrier 1 of less than 0.4, the cleaning member 30 having a dynamic friction coefficient μ1 with respect to the image carrier 1 of 0.4 or more has suitable cleaning performance. It can be said that.

Considering these results, if the dynamic friction coefficient of the contact charging member 2 itself with respect to the image carrier 1 is large, the total amount of transfer of deposits between the contact charging member 2 and the image carrier 1 increases, The total amount of the adhered substances transferred to the cleaning member 30 also increases, the clogging of the pad 31 and the smoothing of the contact surface due to the adhered substances are promoted, and the cleaning member 30 deteriorates quickly. Therefore, the dynamic friction coefficient μ2 of the contact charging member 2 with respect to the image carrier 1 is made as small as less than 0.4 to reduce the total transfer amount of deposits between the contact charging member 2 and the image carrier 1. It is preferable to suppress deterioration of the cleaning member 30.

On the other hand, between the contact charging member 2 and the cleaning member 30, if the dynamic friction coefficient μ1 of the cleaning member 30 with respect to the image carrier 1 is increased as described above, the adhered substances are transferred to the cleaning member 30. It will be easy. Therefore, the coefficient of dynamic friction μ1 of the cleaning member 30 with respect to the image carrier 1 is preferably 0.4 or more.

[0042]

As described above, according to the present invention, the performance of the cleaning member 30 with respect to the contact charging member 2 can be objectively grasped from the relationship between the cleaning member 30 and the contact charging member 2, and is always appropriate. The contact charging member 2 can be cleaned in this state. Further, in the invention of claim 2, the criterion for suppressing the transfer of the adhered substances from the image carrier 1 to the contact charging member 2 becomes clear in the relationship between the contact charging member 2 and the image carrier 1, and the cleaning member. The cleaning performance of 30 can be maintained for a long period of time.

[Brief description of drawings]

FIG. 1 is a configuration diagram illustrating an outline of an image forming apparatus.

FIG. 2 is a partially sectional front view showing a configuration example of a contact charging member 2 of the same device.

FIG. 3 is a schematic front view for explaining a method of measuring a coefficient of dynamic friction of the contact charging member 2 and the cleaning member 30 with respect to the image carrier 1 performed in the embodiment of the present invention.

FIG. 4 is a number line showing the relationship of the dynamic friction coefficient of the contact charging member 2 and the cleaning member 30 with which the image carrier 1 can be expected to have suitable cleaning performance.

[Explanation of symbols]

 1: Image bearing member 2: Contact charging member 3: Eraser 4: Developing unit 5: Transfer member 6: Cleaning blade 7: Eliminating means 8: Mirror 9: Registration roller 21: Shaft core 22: Intermediate layer 23: Surface layer 24: Bearings 25 and 33: Pressing spring 26: Power supply 30: Cleaning member 31: Pad 32: Back plate 40: Tape material

Claims (2)

[Claims] 1. A charged state, comprising: a contact charging member that contacts the surface of the image carrier to charge the surface, and a cleaning member that contacts the surface of the contact charging member to clean the surface. In an image forming apparatus which forms an electrostatic latent image on an image carrier and then visualizes the electrostatic latent image by a developing means and transfers it to a transfer material, the dynamic friction coefficient of the cleaning member with respect to the image carrier is determined by An image forming apparatus characterized in that a coefficient of dynamic friction of a charging member with respect to an image carrier is made larger. 2. The image forming apparatus according to claim 1, wherein the dynamic friction coefficient of the contact charging member with respect to the image carrier is 0.
The image forming apparatus is characterized in that the coefficient of dynamic friction of the cleaning member with respect to the image carrier is set to 0.4 or more while being less than 4.